The present invention is motivated by desirable new applications which require channel-associated signalling facilities which were not anticipated in the original DS3 signal specification. Examples of such applications are (i) DS3 functional compatibility with new Sonet and Syntran signal formats which include dedicated signalling fields for advanced network maintenance and control functions; (ii) return path signalling for closed loop digital radio techniques such as intelligent antenna control and adaptive transmit power control; and (iii) signal-associated restoration signature transport to implement a distributed realtime network restoration with new digital cross-connect machines.